MARSEILLE (Reuters) - Russians trained to fight were involved in the worst of the fan violence that erupted in Marseille during the opening of the Euro 2016 soccer tournament, the French city's chief prosecutor said on Monday.

"There were 150 Russian supporters who in reality were hooligans," Brice Robin told a news conference. "These people were well prepared for ultra-rapid, ultra-violent action. These are extremely well trained people."

Robin said some Russian supporters were turned back on arrival at Marseille's international airport but that others had arrived overland.

Most of the 35 people who were injured in the fighting were English, the prosecutor said, adding that two Russian nationals were being expelled from the country.

(Reporting by Jean-Francois Rosnoblet in Marseille and Brian Love in Paris; writing by Richard Lough; editing by John Stonestreet)